Preparation and Performance of the Self-powered Ultraviolet Photodetector Based on the Bi2O3/g-C3N4 Composite
Self-powered Ultraviolet(UV)photodetectors have attracted great attention for the fast detection of UV light without external bias voltage,as well as for their high sensitivity,light weight and low energy consumption.In order to obtain high-performance self-powered UV photodetector,Bi2O3 nanoblocks and g-C3N4 nanosheets were synthesized by thermal polymerization method.Subsequently,Bi2O3/g-C3N4 composites were prepared via solution method,and their morphology,crystal structure,chemical composition and valance state were characterized.The results of morphological characterization show that Bi2O3 present as a honeycomb-structured block,which are attached to the surface of g-C3N4 nanosheets with layered structure.The characteristic peaks of Bi2O3 nanoblocks and g-C3N4 nanosheets can be observed in the XRD pattern of the as-prepared composite,indicating successfully constructing of the Bi2O3/g-C3N4 heterojunction.Further,XPS measurement of the Bi2O3/g-C3N4 composite was performed to study the valence states of the elements compositing the composite,in which the results of high-resolution XPS of Bi 4f,O 1s,C 1s and N 1s also confirm the prepared composite as Bi2O3/g-C3N4 heterojunction.Based on the as-prepared Bi2O3/g-C3N4 heterojunction,the UV photodetector that can operate without an external power source was fabricated.At zero bias voltage,the photodetection performance of the Bi2O3/g-C3N4 UV photodetector was investigated under darkness and UV illumination by repeating 10 s with light on and 10 s with light off.When irradiated with UV light,the Bi2O3/g-C3N4 UV photodetector immediately generates photocurrent and rapidly rises to the maximum value(0.43 μA)and remain stable.After turning off the UV light,the photocurrent immediately decreases and returns to the initial state.Notably,the maximum photocurrent of the device remains essentially unchanged after 7 cycles,indicating that the Bi2O3/g-C3N4 UV photodetector has good stability and repeatability.In addition,the performance of the UV photodetector prepared based on Bi2O3 nanoblocks was also investigated under the same conditions.The results show that when the Bi2O3 nanoblocks UV photodetector was exposed to UV light,its photocurrent can rise rapidly to reach the maximum value of about 0.21 μA.Remarkably,the maximum photocurrent of the Bi2O3/g-C3N4 UV photodetector is enhanced by about 1.05 times compared with that of the Bi2O3 nanoblocks UV photodetector.And the Bi2O3/g-C3N4 UV photodetector exhibits a fast response time(～181.7 ms),which demonstrates that the device is capable of stable and fast detection of UV light.The photoresponse characteristics of the Bi2O3/g-C3N4 UV photodetector were also investigated under UV light irradiation with different intensities.It is found that even under UV irradiation at a lower light intensity(2 mW/cm2),the photocurrent generated by the device increases rapidly as well as still reaches a maximum value of about 0.098 μA.And there is no significant attenuation of the maximum photocurrent after several cycles of cycling.Meanwhile,note that the photocurrent increases approximately linearly with the increase of the light intensity,which indicates that there has a well linear relationship between the photocurrent and incident light intensity.And the device also exhibits excellent recyclability and stability for the detection of UV light of different intensities,which demonstrates the ability of the device to achieve effective detection of UV light over a wide range of UV intensities.The device also exhibits a large switching ratio with a value of about 1 313,which demonstrates the high sensitivity of the Bi2O3/g-C3N4 UV photodetector.And its responsivity is as high as 0.17 mA/W under UV irradiation of 2 mW/cm2,demonstrating the potential application of the device in the field of photodetectors.In addition,the detection mechanism of the Bi2O3/g-C3N4 UV photodetector is analyzed.The high-performance Bi2O3/g-C3N4 self-powered UV photodetector prepared in this work may be used in the field of future optoelectronic devices.
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